10.5 Combination functions

Function: int gsl_combination_next(gsl_combination * c)

This function advances the combination c to the next combination
in lexicographic order and returns GSL_SUCCESS. If no further
combinations are available it returns GSL_FAILURE and leaves
c unmodified. Starting with the first combination and
repeatedly applying this function will iterate through all possible
combinations of a given order.

Function: int gsl_combination_prev(gsl_combination * c)

This function steps backwards from the combination c to the
previous combination in lexicographic order, returning
GSL_SUCCESS. If no previous combination is available it returns
GSL_FAILURE and leaves c unmodified.